@caylalayman‘s advice is good: start out with simple songs you know well.
Generally with ear training, using music you like is a great way to boost your motivation and interest levels – but it’s important to hit the right difficulty level too, as if the task is too hard then the resulting frustration will sap your motivation right back down!
As with playing by ear, it’s important to choose tracks which suit your current ability levels and focus. If you’re practising recognising major and minor chords and working on major scale solfa, then trying to transcribe a far-out performance of a jazz standard, or a discordant metal track is not going to end well! Much better to choose a simpler song (pop and rock tend to work well, especially if you’re focusing on recognising I-IV-V progressions) and build from there.
One more tip: choose a “dream track”: a track you love but which you know is musically difficult, and set that as your goal in learning to transcribe, something you know you can’t do now but will be working towards.